The present invention relates to decapsulation of an encapsulated object. The invention includes a system and method for etching away (“decapsulation”) the plastic or epoxy material encapsulating an object, such as a semiconductor or integrated circuit component, for purposes that can include visual inspection and/or failure analysis.
Plastics and plastic-like materials have been used to encapsulate electrical components, including semiconductor devices, for many years. To provide a plastic packaging around an object epoxy resin is typically molded around the object. For example, epoxy resin is molded around a semiconductor die and the lead frame on which the semiconductor die is attached, including the bonding wires or other connections between the die and the lead frame. Once encapsulated, however, an internal visual inspection or internal probing of the interior of the encapsulated object is not possible. Consequently, removal of the epoxy is often desired to allow for inspection or testing of the encapsulated object, particularly in the case of failure analysis.
Typically, the component to be decapsulated is heated on a hotplate or other heating device. The type of acid and etch temperature is selected based on the properties of the material to be etched, since it is known in the art that different encapsulation materials react with some acids better than others. Suitable acids include fuming sulfuric or fuming nitric acid. Fuming sulfuric acid requires a high temperature of approximately 300 degrees Celsius whereas fuming nitric acid requires a high temperature in the approximately 100 degree Celsius range.
Commonly, concentrated acids, such as sulfuric acid and nitric acid, or other solvents for the specific resin have been employed, depending on the type of resin to be removed. Significant amounts of acid are dropped onto the heated component, which causes a reaction with the encapsulating material that removes the encapsulating material from the object. Waste material from the component is then rinsed away using acetone or another suitable procedure. Then the process is repeated, with the heating of the package and then more acid being dropped on the area of the encapsulating material to be removed. The procedure is repeated until the object is decapsulated; in this example, the semiconductor die and/or lead frame connections are exposed.
One problem experienced in the commonly used procedure is that heating the semiconductor component may alter its physical and electrical characteristics. This is particularly true if the component has been attached to a printed circuit board since heating the entire board can easily damage or alter the characteristics of the board and surrounding components.
Accordingly, it is an object of this invention to provide a controllable method of selectively removing the encapsulating material including system and method for the “spot” removal of the encapsulating material from a selected area of the encapsulated object.